Changes in red wine soluble polysaccharide composition induced by malolactic fermentation.

The polysaccharide content of wine is generally assumed to originate from grapes and yeasts, independent of bacterial metabolism, except for the action of certain spoilage species. This study shows that malolactic fermentation (MLF) significantly modifies the soluble polysaccharide (SP) concentration of various red Bordeaux wines. Wines with the highest initial SP concentration go on to present decreased SP concentration, whereas those with the lowest initial SP concentration rather go on to have a higher SP concentration after MLF. These tendencies were observed whatever the Oenococcus oeni strain (indigenous or starter) used for MLF. Neutral and charged SPs were affected, but to a degree that depended on the microorganisms driving the MLF. The SP modifications were directly linked to bacterial development, because non MLF controls did not present any significant change of SP concentration.

A putative glucan synthase gene dps detected in exopolysaccharide-producing Pediococcus damnosus and Oenococcus oeni strains isolated from wine and cider.

Some lactic acid bacteria can induce viscosity in wine, beer and cider by production of exopolysaccharides (EPS). A polymerase chain reaction (PCR) assay was previously described for the detection of ropy Pediococcus damnosus strains in wine [J. Appl. Microbiol. 90 (2001) 535]. The primers used in that study, PF5 and PF6, are investigated in addition to new primers which broaden the range of spoiling agents detectable by PCR. Primers PF1 and PF8 allow the amplification of DNA from ropy P. damnosus strains isolated from wine, as was observed with PF5 and PF6. In addition, PF1 and PF8, unlike PF5 and PF6, are able to generate an amplicon using template DNA from a ropy P. damnosus strain isolated from cider and a ropy Oenococcus oeni strain isolated from champagne. Two different ropy Lactobacillus species were also isolated, but their DNA was not amplified using primers PF1 and PF8. The new primers PF1 and PF8 were chosen from the sequence of gene dps, a putative glucan synthase gene, found across all the ropy P. damnosus strains isolated, from both wine or cider, and also in a ropy O. oeni strain. To our knowledge, this is the first time that an EPS-producing O. oeni strain is described. Glucan biosynthesis was assessed by agglutination tests done with Streptococcus pneumoniae type 37-specific antibodies, which specifically detect glucan-producing cells. The results show that there is a direct correlation between glucan production and detection of gene dps. Therefore, Dps is considered a candidate for the glucan synthase enzyme responsible for EPS production by ropy strains of P. damnosus and O. oeni.